Debit order reversal & charges

I changed my salary details with my emplyer and I am no loner earning through Nedbank. When I checked my balance on the 26th of November I noticed that I have a negetive balance due to debit orders that went throguh to Nedbank. I funded my account immidiately to prevent reversal of the debit orders as the balance was still negetive. Afterwardsmy balance was no longer negetive. When I logged on to my internet banking today I noticed that the debits were reversed after I deposited the money and a total amount of R500 was charged to my account. What I want to know is why do you mislead the consumers then and make it seem like the transactions went through after depositing the money while you are actually aiming at milking the account owner dry for each and every deposit. I have never had this kind of problem previously with my account and charging me R500 even though I rectified the problem is unfair. Now I dont even know why I should keep my account with Nedbank because this is purely an error on your side.